The visceral human leishmaniasis or “kala-azar” in the Americas and the Mediterranean is a known canine zoonosis. Blood-sucking insects acquire the etiologic agent by feeding themselves from wild canids and subsequently transmitting it to domestic dogs. Transmission to humans by sandflies causes visceral human leishmaniasis, a serious disease that can be fatal if not treated properly.
Roughly 500,000 new human cases of kala-azar are reported annually worldwide. A protective prophylactic vaccine against human disease is not yet available. The best performance to date has been achieved with an experimental first-generation vaccine that induced 12% protection among people who converted to positive in an intradermal test for the lysate of Leishmania (IDR) after vaccination is completed. Thus far, chemotherapy against kala-azar has proved to be highly toxic and not always effective.
Leishmania (L.) chagasi and Leishmania (L.) infantum are the etiological agents of human visceral leishmaniasis (HVL) in America, in the Mediterranean, Middle East and Asia. It is a severe and often lethal disease if not treated soon after onset of symptoms. In these regions, the disease is a canine zoonosis. The parasites are exposed on the skin of dogs, foxes, and wild dogs, and are transmitted to humans via a transmission cycle involving insects and sandflies.
Zoonotic Visceral Leishmaniasis (ZVL) is a re-emerging canine zoonosis, whose epidemiological control involves the slaughter of seropositive-infected dogs, treatment of domestic and peridomestic environments with insecticide, and systematic the treatment of human cases. Brazil is one of the four countries where 90% of the human cases occur. As a control method, the slaughter of seropositive dogs is practiced in Brazil and China; however, it is not accepted in Europe. The canine control programs are extremely difficult, costly, and require permanent surveillance and sensitive serological diagnostic methods to be effective. Furthermore, as many seropositive dogs are asymptomatic, the campaign is complicated, although the infectiousness of asymptomatic dogs for vector insects has been demonstrated.
Treatment of homes with insecticides and preventive vaccination of humans and dogs against visceral leishmaniasis are presently regarded as the best tools provided for control and eradication of the disease and reduce both the human and canine cases. Although several vaccines have been tested under experimental conditions, only some showed efficacy in field tests against the challenge of natural infection, and only Leishmune® vaccine is currently licensed in Brazil, as a prophylactic vaccine against canine visceral leishmaniasis.